Power systems can have one or more generators or engines for supplying electricity to electric power loads. For example, a single generator or engine may drive multiple traction motors, where the motors may be switched by switch gear between an in-parallel configuration and an in-series configuration. Alternatively, a transition wiring system may connect multiple engines or generators to traction motors. The use of a transition wiring system allows each generator to be sized to provide half of the maximum voltage and half of the maximum current needed, providing a significant savings on engine or generator costs, and reducing emissions. The transition function can be accomplished by the wiring between the engines or traction generators and the traction motors. Typically two contactors are used to switch the generators between in-series and in-parallel configurations. At low ground speeds the two contactors are de-energized and the traction energy is low-voltage, high-current. When the locomotive reaches the transition speed, the contactors are energized, and the traction energy is high-voltage, low-current.
U.S. Pat. No. 6,984,946 to Donnelly et al. (“the '946 patent”) discloses a locomotive with a plurality of battery racks arranged in-parallel, with the additional capability of providing some or all of the electrically switched battery racks in-series with other battery racks. The capability to switch to an in-series arrangement of battery racks disclosed in the '946 patent includes using solenoids or relay-operated contact switches, which can be operated manually or by logic control. Switching from in-parallel configuration to in-series configuration in the '946 patent allows 50% more voltage to be supplied, but has 50% less ampere-hour capacity than the battery racks configured in-parallel.
The design of the locomotive in the '946 patent may have certain disadvantages. For example, either the contactors must be large enough to break the current running through the contacts to switch between in-series and in-parallel configurations, or the excitation current of the battery racks must be driven to zero before opening the contactors. Contactor size is generally chosen to allow the contactor to carry the current, not break a high traction current. Also, reducing the draw on the battery racks during transition slows down the transition process and may create a surge through the draught gear and couplings.
U.S. Pat. No. 4,328,427 to Bond (“the '427 patent”) discloses a locomotive with an AC power supply with two sets of duplicate windings with switching means to change the alternator windings from parallel to series (or vice versa). The capability to switch between in-series and in-parallel disclosed in the '427 patent includes using two switching means, such as contactors. Switching from in-parallel configuration to in-series configuration in the '427 patent allows approximately 50% more voltage to be supplied, but has approximately 50% less ampere-hour capacity than the windings configured in-parallel.
The design of the locomotive in the '427 patent may have certain disadvantages. For example, either the contactors must be large enough to break the current running through the contacts to switch between in-series and in-parallel configurations, or the excitation current of the battery racks must be driven to zero before opening the contactors. Contactor size is generally chosen to allow the contactor to carry the current, not break a high traction current. Also, the AC power supply must be large enough to supply the maximum current draw of the traction motors when the windings are configured in-series and to supply the maximum voltage draw of the traction motors when the windings are configured in-parallel.
The transition wiring system and methods of the present disclosure solve one or more of the shortcomings set forth above.